Unraveling the Degradation Mechanism of FIrpic-Based Blue OLEDs: I. A Theoretical Investigation

We report a detailed ab initio study of the of the microscopic degradation mechanism of FIrpic, a popular blue emitter in organic light-emitting diode (OLED) devices. We simulate the operando conditions of FIrpic by adding an electron-hole pair (exciton) to the system. We perform both static calculations with the time-dependent density functional theory framework, and we also simulate the evolution of the system at finite temperature via Car-Parrinello molecular dynamics. We found triplet excitons are very effective in reducing the Ir-N bond breaking barrier of the picolinate moiety. After the first bond breaking, the two oxygens of picolinate swap their position and FIrpic can either remain stable in an "open" configuration or loose a picolinate fragment, which at a later stage can evolve a CO2 molecule. Our method can be applied to other light-emitting Ir complexes to quickly estimate their stability in OLED devices. In Paper II, we complement our theoretical study with a parallel experimental investigation of the key degradation steps of FIrpic in an aged device.